Carrier current telegraph system



Jan. 15, 1935. J. R. HYNEMAN 1,937,938

CARRIER CURRENT TELEG RAPH SYSTEM Fil ed on. 21, 1932 FIG; I

AMP

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I 4s v 49 7 5o 5| 52' INVENTOR J. R. HYNEMA BY j ATTORNEY Patented Jan. 15, 19 35 UNITED STATES PATENT OFFICE mamas I caltmaa warms-r ransom srsreu' John a. Hyneman, Chatham, N. 1., aslignor to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Application October 21,1932, Serial No. 638.985

12 Claims. (01. 178-68) of groups or trains of current alternations of pre-determined frequency.

The invention is applicable to land line transmission over a wide range of frequencies, but is particularly suitable to the relatively low frequency type of carrier systems, such as are commonly employed on submarine cables.

For instanceon certain trans-Atlantic submarine cable routes a relatively low speed, long span cable extending across the Atlantic may be connected at each end to a short section capable of operation at a higher speed. During through transmission the signal speed on the short sections is necessarily restricted to the operating speed of the longer section, although the short end sections-may be capable of operation at frequencies up to one hundred cycles or more. Therefore, in order to reduce the number of short sectionsrequired and provide spare channels in case of failure of a short connecting section, it has been proposed to provide a carrier channel in each direction over the short sections in addition to the regular direct current channel. The current required for carrier operation over the short cable sections-is relatively high, however, of the magnitude of one half ampere. and is not readily obtained by means of vacuum tube amplifiers.

Heretofore it has been the practice to apply the output of the carrienfrequency generator directly to the cable and to control the level thereof by controlling the field of the generator, or to open and close the entire output current of the generatorby means of a transmitting-key or relay.

r A primaryobject of the invention is to'employ a gaseous conduction tube for the reception of alternating current signals.

Another objectis to adapt a device normally ceived alternating current signal.

Another object islto provide a carrier current telegraph system in which the power output to the line may be large and whic lrinay be con trolled by a keying circuit employing a relatively low current.

Another object of the invention is to-provide a carrier current telegraph system in which the voltage.

received code impulses will be of uniform duration and correctly phased.

A further object is to enable the carrier frequency to be impressed upon the line in correct phase relation to the operation of the keying mechanism and more specifically to open and close the transmitting circuit at the preferred point of the cycle.

Other objects and advantages of the invention will hereinafter appear. s

In accordance with my invention I employ at the transmitting station, a commutator operating in synchronism with thetransmitting distributor and having an output of small amplitude which controls the discharge from gaseous conduction tubes ofa type which are capable of passing a relatively large amount of current. The characteristics of the gaseous tubes are such that they normally interpose a high resistance in the circuit in which they are connected, this resistance being broken down by a relatively small current in the auxiliary or control circuit, the tube then being capable of passing a large amount of current. V

A type of tube which I have found particularly satisfactory for this purpose is described in an article by Dr. Albert W. Hull, entitled "Hot Cathode Thyatrons" and published in the General Electric Review, Vol. 32, #4, of April, 1929, at page 213, This type of tube is in eifect an electrostatically controlled arc rectifier and briefly consists of a gas filled envelope containing then occurring,'wiil allow a large amount of current to fiow from the anode to the cathode.

The tube is unlike the ordinary three electrode vacuum tube or audion in that as soon as the plate currentvstarts, the grid has no further influence on the plate current and the discharge can only be stopped by removing or reducing the plate Two suchdevices are arranged to opera-teas an inverter their input circuit being coupled to the commutator and transmitting distributor in such manner that the gaseous conduction devices operate alternately during reversals of current. The output of the gaseous conduction devices is applied to a transformer, the secondary winding of which is connected to a line through a filter which serves to eliminate the higher harmonic frequencies normally present in the square top wave from the commutator.

At the receiving station the signals arerectified or detected and applied to the grid of a single gaseous conduction tube havinga rotary distributor connected in the output circuit whereby, as the distributor brush rotates in synchronism with the transmitted signals, the output'circuit of the tube will be interrupted between each signal and the signal will be regenerated so that substantially perfect signals will be supplied to the receiving printer.

The system may be either start-stop or multiplex and in the latter case the printer circuit may be arranged so that the printers associated with each alternate channel will operate on the received oscillations as marking signals and those associated with the intermediate channels will operate on the received oscillations as spacing signals.

In order that the invention may be more fully understood reference will be had to the accompanying drawing in which:

Figure 1 is a circuit diagram showing the transmitting apparatus for a carrier current channel embodying my invention, in this case adapted for handling a regular multiplex printing telegraph circuit, and

Figure 2 shows diagrammatically the associate receiving system.

Figure 3 is a circuit diagram of a modified receiving arrangement.

The transmitting apparatus shown in Figure l comprises-a suitable transmitter 10 which may be either a manually controlled transmitter, or a tape controlled transmitter, such as is described in patent to G. R. Bem'amin, No. 1,298,440, granted March 25, 1919, and entitled Automatic transmitter. The transmitter is diagrammatically illustrated as comprising a plurality of stationary grounded contacts 11 and a group of movable contacts numbered 1 to 5. The contacts 1 to 5 are connected to the correspondingly numbered segments of ring 12, of a multiplex distributor TD. A solid ring 13 is associated with the segmented ring 12. The distributor preferably has a second set of rings comprising a solid ring 14 and a segmerited ring 15, the number of segments of the latter ring being an even multiple of the number of segments of the ,transmitting ring 12. The alternate segments ofiring 15 are strapped together and connected to one polarity of the battery 16 and the remaining segments are connected to the opposite pole of the battery. The midpoint of the battery is grounded. Brushes B1 and B2 traverse the rings 12, 13 and 14, 15 respectively, in unison. Solid rings 13 and 14 are connected respectively to the opposite ends of the primary winding 17 of a transformer 18. 4

In transmitting a single character code combination, the contacts 1 to 5 of the transmitter 10 are set up in accordance with the combination, thereby grounding pre-determined segments of ring 12. Upon engagement of the brush B1 with the grounded segments current reversals occur in the winding 17 and during the engagement of the brush with the ungrounded segments, the circuit of the winding 17 is open.

The current reversals produced in the windings of the transformer 18 may be of low amplitude and therefore readily interrupted on the segments of ring 12. In order to increase the output of the transmitter, I employ an invertor comprising two gaseous'conduction tubes 21 and 22 which maybe of the type described in the aforesaid article by Hull type or other type having similar characteristics thereto, each tube having a positive electrode or anode 23, an electron emitting cathode 24, either of the directly or indirectly heated type, and a grid 25, enclosedwithin a gas filled envelope. The input and output circuit of the tubes 21 and 22 are arranged so that upon the application of a critical potential to the grid of one of the tubes, a

discharge is initiated therethrough, which causes the discharge to cease in the other tube. Thus by alternately applying a starting potential to the grids of the two tubes, they may be caused to operate alternately. The cathodes 24 of the two tubes are connected together and to the negative termirial of a battery or other source of potential 26. The anodes 23 are connected through resistances R1 and R2 to the opposite terminals of the primary winding 27 of an output transformer 28 and are directly bridged by a condenser 29. The midpoint of the winding 27 is connected to the positive terminal of the battery 26. The grids 25 of the gaseous discharge. tubes are connected to the opposite terminals of the secondary winding 30 of the transformer 18, the midpoint of which is joined through a stabilizing battery 31 to the cathodes of the tubes. The secondary winding 32 of the output transformer is connected to the outgoing line circuit L through a suitable transmitting filter 33.

The operation of the inverter is as follows:

With segment 1 of ring 12 grounded, as the brush B1 passes thereover, current reversals are produced in the winding'of the transformer 18 and the grids of the tubes 21 and 22 are alternately rendered positive. Assuming that on the first half cycle the grid of tube 21 is made positive, the internal resistance of this tube will be decreased and a discharge initiated therethrough, the current flowing from the positive terminal of the battery 26 through the lower half of the winding 27 of the output transformer and resistance R1 to the anode of tube 21, and thence from the cathode thereof back to the battery 26. A current is thus induced in the line circuit L, through the filter 33, in a definite direction. The tube 21 continues to operate as long as positive potential is applied to the anode thereof, independently of the grid 25 and until the beginning of the next current reversal through the transformer 18, at which time the positive charge is removed from the grid of tube 21 and a similar positive charge applied to the grid of tube 22. Tube 22 therefore starts to operate, permitting current to flow from the positive terminal of the battery 26 through the upper half of the winding 7 of transformer 28 in the opposite direction. The condenser 29 which was previously charged from the tube 21, is now subject to a displacement current in the opposite direction andtherefore discharges in' such a direction as .to momentarily reduce the voltage in the plate circuit of the tube 21 sufficiently to permit the tube to become deionizedand interrupt the flow of current therethrough. The tube 22 continues to operate, inducing a current in the line circuit L in the reverse direction from that' induced due to the operation of the tube 21; Alternations are thus .sent over the line circuit L at a frequency determined by the rate of passage of the brush B2 over the segments of ring 15.

If the second intelligence signal, controlled through contact 1 of the transmitter, is of markceiving apparatus ope ingcharacter, a second train of oscillations will be transmitted overthe line circuit L, the number of reversals or cycles comprising the marking signal depending of course upon the number of segments of ring 15 traversed by the brush B2 I while the brush-B1 ispassing over a segment of ring 12.

Assuming the second intelligence signal to be open and the grids of both tubes 21 and 22 will remain below the critical starting potential under the influence of the stabilizing battery 31. The particular tube operating at theend of the preceding marking. signalwill continue to operate during the spacing period, butsince the dischargeis of a continuous nature, no current will be induced in the line circuit L. Also since each segment of ring 12 encompasses an even number of segments of ring 15 the initial reversal will always be of the opposite polarity from the terminating reversal of the last marking segment so that the idle tube will always be effective to transmit the initial half wave to line. In cases where the current requirements can be met by the distributor alone without the inverter tubes, an uneven number of half waves may be used'for a signal.

In the output of the transformer 28 a transmitting filter 33 of well known type should be employed for the purpose of purifying the wave to prevent interference to other channels operating at other frequencies on the same or contiguous cables. Therefore, each marking signal is trans-- mitted over the line circuit as a-train of oscillations and the spacing signals as no current intervals.

It will be noted that due to the positive drive connection between the brushes B1 and B2 (both being mounted on the same shaft) that each group of oscillations produced by grounding one of the segments of ring 12 contains a uniform number of alternations (ten each in the embodiment shown), the oscillations being in phase with the transmitted signals, that is, the circuit being opened and closed only at the time the oscillations pass through the zeropoint. Each marking signal, therefore, consists of a uniform number of whole impulses or half cycles. This latter feature is important in carrier telegraph systems since when the'cir'cuit i s opened and closed indiscriminately and at other than the zero point, a severetransient is transmitted into the cable which may interfere with the direct currentreting on the same cable. Further, at the receiving end the mutilated half cycles at the start and finish ofthe signal may be received imperfectly thus causing a fortuitous shortening and lengthening of the signal. I

twovacuum tubes 38 and 39 having their grids connected to the opposite terminals of the secondary'winding of the transformer 3'7 and the cathodes connected through the biasing battery 40 to the mid-point of the secondary winding of the transformer. Although the thermionic rectiflers are illustrated here other types also will servev satisfactorily. The plate circuits of the tubes 38 and 39 are coupled to the input circuit of-a gaseous conduction tube 41 through the impedance R3. The grid of the tube 41 is normally main tained below the critical starting potential of the tube bythe stabilizing battery 42, Whenever a discharge occurs ineither of the tubes 38 or 39 a positive potential is applied to the grid 43 due to the potential drop across the impedance R3.

The anode 44 of the tube 41 is joined to the solid ring 45 of a receiving distributor RD and'the cathode 46 is connected through the battery 47 to one terminal of the windings of the selecting magnets 48 to 52 to a multiplex printer, the opposite terminals of these magnets being connected vtothe segments 1 to 5 .of the receiving ring 53 of the distributor. The brush B3 passesacross the segments 1 to 5 in substantial synchronism with the transmittedgroups of oscillations.

As the brush BS engages segment 1, during the reception of the first train of oscillations, the grid of the tube 41 will be raised above the critical starting potential through the action of the rectifler, irrespective of whether the particular half cycle being received at the time isof positive or negative polarity. Consequently the tube 41 will immediately start to operate, the circuit being completed from the anode 44, through ring 45, brush B3, segment 1, selecting magnet 48 and battery 4'7 to the cathode 46. As the brush passes on to the dead segment following segment 1, the plate circuit of the tube 41 is interrupted and the discharge through the tube ceases. As the brush now passes on to segment 2, if a marking signal is being received over the line a second discharge starts through the tube 41 thereby operating'the selecting magnet 49. However, if a spacing signal or no'current interval occurs at this time tube 41 remains unoperated and the selecting magnet unenergized. The discharge through the tube 41 is interrupted after each signal and before the reception of the succeeding signal train as the brush B3 passes over the intermediate dead segments.

The. live segments of the receiving distributor are of such width as to correspond to the central portion only of each train, of received oscillations thereby insuring that the received signals will be of sufficient strength to initiate a discharge through the tube 41 as the brush engages the live segments of the distributor.

By the use of the three element detector the alternating current signal is converted into a direct current'signal quite similar in its char-- ties connected to the ringsof the sending dis- ,1

tributor' and so is preferable to a single wave device. The rectifier also adapts the system for transmission by the Morse or other similar two elementxcode. The Morse key in conjunction with one of the well known methods for opening and closing the circuit at a no -current period should be substituted in place of the transmitter 10 and distributor rings 12 and 13. At the receiving end the single gaseous conduction tube but without the distributor RD will not interrupt the circuit during spacing intervals. ;Therefore the single tube should be replaced by a pair of tubes connected in inverter fashion as shown in Fig. 3.

The plate circuits of tubes 38, 39 are coupled to the input circuit of two gaseous conduction tubes 54 and 55 through impedance B3. A filter or shaping device F is inserted in the output circuits of tubes 38 and 39 to remove the A. C. component of the rectified signals. Tube 54 has its grid normally biased positive by battery 56" and tube 55 has'its grid biased negative by battery 57. A battery 58 is arranged to normally oppose the plate battery 59 of tubes 38, 39. When no signals are received over the line the points 60 and 61 of the circuit are at zero potential, due to the opposing eifect of batteries "58 and 59. Consequently, tube 54 is operated (due to its positive grid) and tube 55 is unoperated. Whenever a train of oscillations is received, causing a fiow of direct current across the impedance R3, the point 60 becomes negative and the point 61 positive, relative to the cathodes of the tubes 54 and 55 thereby overcoming the biasing efi'ect of the batteries 56 and 5'? and reversing the'charges on the grids of these tubes. The tube 55 is thus caused to operate. The tubes are connected in inverter arrangement through the resistance R4 and condenser 0, whereby the starting of the discharge through one tube interrupts the discharge through the other. Consequently, the tube 55 is caused to operate during the reception of a signal train, that is during the receptionbf a dot or dashof Morse code, and the tube 54 is caused to operate during a spacing signal. A sounder S, operated byrelay 56 included in the output circuits of tubes 54 and 55, responds to the Morse signals.

It can be seen that if the rectifier tubes 38, 39 were not provided the inverter tubes would respond in rapid succession to the alternate half waves of the marking signals instead of responding alternately to the marking and spacing signals respectively.

Inasmuch as the gaseous conduction tubes of the type mentioned of moderate size are capable of passing large currents, of several amperes,

' under the control of feeble currents, the present system is particularly adaptable for carrier current telegraph systems which require the transmission of large amplitudes.

While I have shown the invention with particular reference to a multiplex telegraph system it is to be understood that it is equally applicable to a start-stop system. In this case also means should'be provided to start the transmitting distributor at the zero point of each alternation produced by the commutator ring 15.

It is understood that the system described can be superimposed on a submarine cable or other signaling circuit carrying a regular direct'current transmission channel, and that a number of such systems each employing a separate frequency may be operated simultaneously over said circuit.

It is obvious, of course, that the invention may be embodied in various other forms without departing from the invention and, therefore, I do not desire to be limited to the exact details shown a nd described but contemplate all variations as of current oscillations, a receiving apparatus for said signals comprising an electrostatically controlled gaseous conduction tube and a full wave detector responsive to received oscillations for applying a starting condition to said discharge tube in response to both the positive and negative half cycles of said received oscillations.

3. In a carrier current telegraph system, a source of signals, said signals comprising groups of current oscillations, a multiplex distributor on whichsaid signals are received, a gaseous conduction device having an input and output circuit, means for completing said output circuit through said distributor in synchronism with received os cillation groups and means for applying a starting potential to the input circuit in response to both positive and negative half cycles of said received oscillations.

4. In' a carrier current telegraph system, a source of signals, said signals comprising groups of current oscillations, a receiving apparatus comprising a rectifier for said received oscillations, a gaseous conduction tube controlled by said rectified current, a synchronous distributor in the output circuit of said tube and a receiving instrument controlled by said distributor.

5. In a carrier current telegraph system, a source-of signals comprising groups of current oscillations, a full wave rectifier for said oscillations adapted to produce uni-directional impulses, a trigger device subject to said uni-directional impulses and adapted to be started into operation thereby, and, means operating synchronously with said signals for interrupting the operation of said device.

6. In a carrier current telegraph system, means for transmitting groups of current oscillations, each group comprising a whole number of impulses, a receiving apparatus therefor comprising a full wave rectifier and a gaseous conduction relay adapted to be started into operation by said rectified oscillations, and means independent of said oscillations for interrupting the operation of said relay.

7. In a carrier current telegraph system, a transmitting apparatus comprising a pair of gaseousconduction tubes disposed in push-pull relation, means for producing discharges in said tubes alternately, keying means for starting and stopping said alternate operation of said tubes in accordance with a predetermined code, and means for eflecting said starting and stopping at a frequency which is an even divisor of the frequency of said alternations. I

8. In' a carrier current telegraph system, a transmitting apparatus comprising an alternator,

a distributor operating in synchronism therewith and containing segments, each of which subtends a uniform whole number greater than one of half cycles, and means 'for completing signal circuits serially through said alternator and distributor in accordance with a prearranged code.

9. In a carrier current telegraph system, 'a transmitting apparatus comprising an alternating current commutator, a transmitting distributor operating in synchronism therewith, said distributor serving to make and break the circuit through said commutator in accordance with a prearranged code and in definite timed relation-to each alternation produced by said commutator and a transmitting apparatus controlled by the alternations produced in said circuit.

10. A carrier current telegraph system comprising an arc discharge path for each polarity of current, an input circuit for each discharge path,

a source of current alternations in said input circuits for producing discharges alternately through said paths, 9. ke ing device for said source of alternations, means for opening and closing said keying device assaid oscillations pass through a zero point, a line circuit and means for completing the output of said tubes to said line circuit. 11. In a carrier current telegraph system, a source of carrier current telegraph signals comprising two difierent line conditions, a pair of electrostatically controlled gaseous conduction tubes having control electrodes, said electrodes being so biased that one tube responds to one line condition and the other tube responds to the other line condition and receiving means in the output circuits of said tubes.

12. In a carrier current system, a source of telegraph signals comprising groups of current oscillations, a pair of gaseous conduction tubes, one of said tubes being responsive to current oscillations to produce a discharge therethrough, and the other being responsive to cessation of oscillations to produce a discharge therethrough, whereby said tubes operate alternately, a receiving instrument and means including the output circuit of said tubes for applying steady current conditions to said receiving instrument in response to said received oscillations.

JOHN R. HYNEMAN. 

